| Jars Partnership Limited | Other services | 2018 |
| Jasper Morrison Limited | Administrative & support | 1997 |
| Jaycee Property Management LLP | | 2022 |
| Jaykrish Limited | Real estate | 2012 |
| JB Energytech Limited | Professional & scientific | 2017 |
| Jenvin Properties Ltd | Real estate | 2021 |
| John Bignell Limited | Manufacturing | 1996 |
| John Bray Hastings Limited | Real estate | 2009 |
| JRB Building and Maintenance Limited | Construction | 2010 |
| JRG Chinnor Ltd | Real estate | 2019 |
| Jrsb Investments Ltd | Professional & scientific | 2025 |
| Jsesc Limited | Financial services | 2026 |
| Just BE Property Limited | Real estate | 2023 |
| Just DO IT BDS Ltd | Construction | 2018 |
| Justine Cawley Holdings LLP | | 2022 |
| Justine Cawley Property Archway Ltd | Construction | 2019 |
| Justine Cawley Property Ltd | Construction | 2017 |
| Juxbridge Property Maintenance Ltd | Households | 2020 |
| JWS Ventures (UK) Limited | Other services | 2013 |
| K & R Bartholomew Brickwork Contractors Limited | Construction | 2011 |
| K Whiting Refurbishments Limited | Construction | 2008 |
| K. C. Computers Limited | Wholesale & retail | 2003 |
| K3 Family Investments Limited | Financial services | 2021 |
| K3 Family Management Ltd | Real estate | 2016 |
| K3 Family Partnership LLP | | 2016 |
| K3HP Developments Ltd | Construction | 2023 |
| Kazmethic Consultancy Limited | Real estate | 2019 |
| Kcal Property Ltd | Real estate | 2016 |
| KD (Essex) Limited | Health & social care | 2019 |
| Keith Davey Properties Limited | Real estate | 2016 |
| Kelso Residential Limited | Real estate | 2018 |
| Kensington & Falkner Estates Limited | Real estate | 2015 |
| Kent and Sussex Pool Care Ltd | Other services | 2019 |
| Kent and Sussex Pool Construction Ltd | Other services | 2019 |
| Keshav Properties Limited | Real estate | 2020 |
| Keysure Limited | Administrative & support | 2018 |
| KF Property Developments Ltd | Real estate | 2016 |
| Kiko Property Investments Ltd | Real estate | 2019 |
| Kingham Car Sales Limited | Wholesale & retail | 2007 |
| Kingmore Carpentry Limited | Construction | 2003 |
| Kings Rugby Development Academy | Education | 2017 |
| Kingsley UK Property Ltd | Real estate | 2021 |
| Kinnas Limited | Other services | 2011 |
| Knoyle LLP | | 2012 |
| Koodos Ltd | Information & communication | 2019 |
| Koodos Private Clients LLP | | 2023 |
| Koodos Services Ltd | Financial services | 2024 |
| Koze Property Limited | Real estate | 2024 |
| L E Consultancy (Eastbourne) Ltd | Administrative & support | 2017 |
| L G Projects Limited | Construction | 2017 |
| Laci Land Restoration Ltd | Water & waste | 2016 |
| Lalapanzi Group Limited | Real estate | 2025 |
| Lalapanzi Property Group LLP | | 2016 |
| Lalapanzi Property Investment Ltd | Real estate | 2019 |
| Land of Green Ginger Cafe Bistro Limited | Hospitality | 2010 |
| Land Reserves UK Limited | Real estate | 2007 |
| Larara Limited | Wholesale & retail | 2010 |
| Latchman Mortgage Services Limited | Administrative & support | 2006 |
| Lathia Property Group Limited | Real estate | 2024 |
| Lathia Property Investment Limited | Real estate | 2021 |
| Lathia Property Management LLP | | 2021 |
| Leamington Collective Limited | Wholesale & retail | 2014 |
| Legacy Ventures Ltd | Education | 2006 |
| Lemon & Smith Property Ltd | Real estate | 2012 |
| Lenncourt Limited | Hospitality | 1984 |
| Lennox House Residents Limited | Households | 2012 |
| Leon Property Services LLP | | 2023 |
| Lersuangpen UK Limited | Real estate | 2004 |
| Life Mode Investments Ltd | Real estate | 2023 |
| Lillybank Homes Ltd | Real estate | 2019 |
| Lillybank Limited | Construction | 2005 |
| Lina IT Limited | Information & communication | 2015 |
| Linchpin Commercial Limited | Professional & scientific | 2015 |
| Linnetts Ltd | Real estate | 2022 |
| Liquid Technology (Kent) Limited | Wholesale & retail | 2003 |
| Lisa Harrison Properties Limited | Real estate | 2016 |
| Live to Thrive Property Management LLP | | 2022 |
| LL Cooper Ltd | Real estate | 2026 |
| Llandaff Estates Limited | Real estate | 2021 |
| Loadfast Waste Disposal Limited | Water & waste | 2011 |
| Loeb Developments Ltd | Construction | 2025 |
| London Davis Ltd | Real estate | 2016 |
| London Davis Partnership LLP | | 2016 |
| London Obstetric Healthcare UK Limited | Health & social care | 2015 |
| LOS Flamingos UK Limited | Real estate | 2004 |
| Loud Logistics Global LLP | | 2022 |
| Louise Project Management Limited | Real estate | 2007 |
| Love-Hate Productions Ltd | Information & communication | 2007 |
| LOW Carbon Europe Limited | Professional & scientific | 2013 |
| Lucknow Films Ltd | Information & communication | 2021 |
| Luna Statics Ltd | Wholesale & retail | 2021 |
| M Avaiya Ltd | Professional & scientific | 2023 |
| M C Free Limited | Real estate | 2000 |
| M&S Allen and Sons Limited | Wholesale & retail | 2018 |
| M.B. Properties (Addington) Ltd | Real estate | 2025 |
| M.T. Drains Limited | Construction | 2003 |
| Made Hastings Limited | Real estate | 2016 |
| Madiba Consulting UK Limited | Professional & scientific | 2015 |
| Majors Study Tours Limited | Hospitality | 2004 |
| Maltby Real Estate LLP | | 2023 |